After a previous COVID-19 infection and two doses of Pfizer or Moderna vaccine, the immune systems of some people develop an incredible ability to respond to the virus.
Researchers call this “superhuman immunity” or “hybrid immunity”: the immune system of these patients can produce many antibodies capable of responding to different variants, as documented in several studies in recent months.
In one study, patients with this “hybrid immunity” demonstrated the ability to respond to current variants of concern, non-human coronaviruses, and even new variants that do not yet exist.
Scientists are studying these patients to better understand Covid immunity and immunity to other viruses.
After a Covid infection and vaccination, patients may have “superhuman immunity” to the coronavirus, according to studies. Pictured: Student receives first dose of Pfizer vaccine at a clinic in Long Beach, California, August 2021
“Hybrid immunity” combines the memory of the immune system of a previous Covid infection and vaccination to make the patient super prepared to respond to future coronavirus threats
Pfizer and Moderna vaccines offer incredible protection against Covid.
Of some 173 million Americans completely vaccinated at the end of August, only 10,500 people have been hospitalized with an advanced case and only 2,000 have died from Covid.
These vaccines work by presenting the immune system with a piece of coronavirus genetic material (a piece of mRNA) that teaches the immune system to recognize the virus in case of infection.
People recovering from Covid are also protected against coronavirus, as their immune system remembers how to fight this invader.
And with both mRNA vaccination and a past infection, patients may be overprotected against Covid.
Recent studies have shown that the vaccine and the infected demonstrate “superhuman” immunity, as some scientists have called it.
“These people have amazing responses to the vaccine,” Theodora Hatziioannou, a virologist at Rockefeller University who has studied these patients, told NPR. “I think they are in the best position to fight the virus.”
“These people’s blood antibodies can even neutralize SARS-CoV-1, the first coronavirus, which emerged 20 years ago. This virus is very, very different from SARS-CoV-2,” he said. Hatziioannou.
This is how this works, as immunologist Shane Crotty explains in a June 2021 commentary for the journal Science.
The “natural immunity” of a previous infection works differently from the immunity to vaccination.
In natural immunity, the immune system will create different guarantees against future coronavirus invasion.
This includes B cells and T cells, which are reminiscent of the appearance of the virus and can stimulate the production of antibodies in the event of another infection.
Natural immunity will typically last seven to eight months, according to studies. After about a year, the immune system will still retain some memory, but may be more vulnerable to variants.
However, if someone with natural immunity is vaccinated, vaccination increases the coronavirus memory of their immune system.
If someone with natural immunity is vaccinated, vaccination increases the memory of the coronavirus in their immune system. In the photo: a dose of Johnson & Johnson vaccine is being prepared at a clinic in Los Angeles, California, August 2021
“The immune system treats any new exposure (whether infection or vaccination) with a cost-benefit threat analysis to determine the magnitude of the immune memory that needs to be generated and maintained,” Crotty explains.
As a result, when a person is vaccinated after Covid recovery, the vaccine acts as a signal to the immune system that this virus is a serious problem and that the immune system should devote even more resources to its protection.
This means that there are more B cells and T cells that resemble the appearance of the coronavirus, including B cells that try to predict possible new viral variants.
Crotty calls memory B cells “preventive assumptions by the immune system about what viral variants may arise in the future.”
T cells also help protect themselves from future variants, as the aspects of the virus that T cells recognize are unlikely to change as the virus mutates.
In a study cited by Crotty, the researchers found that previously infected and vaccinated individuals developed 100 times the protective antibodies against variant B.1.351 compared to those who were only infected.
These individuals had much easier immune systems to fight the variant, although they were not previously infected with this variant.
Scientists have observed such a high level of coronavirus immunity both in people who had severe cases of Covid and in those who had mild or no symptoms.
Previously vaccinated and infected individuals (red dots on the right) had a greater ability to respond to different variants of coronavirus, compared with those who were only infected (gray dots on the left).
A recent study by researchers at Rockefeller University, published online as a prepress in August, demonstrates the power of hybrid immunity.
The researchers looked at the immune system preparation of 15 patients who had previously been infected with Covid and then vaccinated, compared with patients who were only vaccinated or only became infected.
They tested blood plasma samples from patients with “hybrid immunity” against six worrying variants of coronavirus, the original SARS virus, and coronaviruses found in bats and pangolins.
For all these different variants, the immune system of patients with “hybrid immunity” was able to recognize the invaders and accumulate antibodies to fight them.
The researchers even tested a new variant of the coronavirus, developed in the laboratory, specifically designed to resist the detection of the immune system. These immune systems could still fight it.
“It could be reasonably predicted that these people will be fairly well protected against most, and perhaps all, of the SARS-CoV-2 variants we are likely to see in the foreseeable future,” said Paul Bieniasz, a virologist at the University of Rockefeller. the study, he told NPR.
“It’s being a little more speculative, but I also suspect they would have some degree of protection against SARS-like viruses that haven’t infected humans yet,” Bieniasz says.
This study, like others that have measured hybrid immunity, was small, and researchers are unsure whether all people who were vaccinated after infection would have the same immune response.
But it is noteworthy that all patients in this study had the same successful response to different variants of coronavirus, Hatziioannou told NPR.
He said vaccinated patients could increase after an advanced case or a third dose of vaccine, although more research on those patients is needed.
“Based on all these findings, it looks like the immune system will end up taking advantage of this virus,” Bieniasz told NPR.
Immunologists aim to hybridize coronavirus immunity more closely, to develop vaccines more successfully against this and other diseases.